An electromechanical watthour meter including an electronic register typically utilizes an eddy current disk which rotates in response to the rate of energy consumption by a load being metered. A shutter is commonly mounted on the same shaft as the eddy current disk, and the shutter is positioned to rotate between a light emitter and a light detector pair. A plurality of circumferential teeth on the rotating shutter sequentially break the light beam between the light emitter and light detector pair to provide a series of electrical pulses, the frequency of which is directly proportional to the rate of energy consumption by the load being metered. The pulses are supplied to the electronic register and, using the pulse data, the electronic register generates well known energy consumption measurements. An example of an electronic demand register is described in U.S. Pat. No. 4,571,692, which is assigned to the present assignee.
Electronic registers are particularly well suited for generating load profile type consumption measurements. To perform load profile operations, the register typically is programmed to store the consumption data, e.g., pulses, in pre-set intervals, e.g., 5, 15, 30 or 60 minute intervals. Since the intervals typically are synchronized around hour boundaries, a real time clock is required. The data for each interval is loaded into a separate register memory location, and then the data is retrieved from the register memory by the utility for billing purposes.
To ensure accurate billing, it is important that the integrity of the load profile data in the electronic register be maintained, even during a power outage. Since the electronic register typically is energized from the power distribution lines supplying energy to the load being metered, if power to the load is lost, the register is deenergized. To prevent loss of the load profile data during a power outage, and upon detection of a power outage, the data is loaded into a non-volatile memory. A back-up battery is supplied with the register and energizes the register microprocessor to enable the register microprocessor to perform the time keeping function during the outage. Since accurate load profile measurements rely upon accurate interval recording, the time of day must be available to the register upon restoration of power after the outage.
The batteries used in electronic registers typically are expensive and add to both the initial cost and maintenance cost of the register. Further, at the end of the battery life, the register battery must be properly discarded to minimize any environmental hazards.
In addition to load profile measurements, other functions performed by electronic registers include communicating metering data and commands between the register and a control station. Examples of such systems are set forth in U.S. Pat. Nos 5,495,239 and 5,459,459, both of which are assigned to the present assignee. Including communications components in a register, of course, adds to the register cost. Such costs may be offset, however, by using such communication capability to provide cost savings and/or productivity gains.
It would be desirable to eliminate the battery used in known electronic registers without sacrificing load profile metering data integrity. It also would be desirable to utilize the communications capability in electronic registers to provide additional cost savings and productivity gains for utilities and others.